The invention relates to a process for hardening ballasts and other heaped structures in situ by means of an adhesive that is pourable at the ambient temperature.
Such a process can be used advantageously wherever ballasting and porous or open-cell heaped structures which are in a loose form or which have already been partially hardened, for example, by means of vibration or stamping operations are to be vertically bonded over a certain height, whereby the pourable adhesive used for this purpose penetrates from the surface of the material down to a certain depth, before it then solidifies and bonds. A particularly important application is the hardening of ballasts used for railroad track systems, which, among other things, serve as sound absorbers and which are at risk due to the high speeds reached by modern trains. The process can also be employed, for instance, to harden construction foundations, emergency roads and auxiliary air strips.
If a high-viscosity adhesive is poured onto such heaped structures, the adhesive cannot penetrate deep enough and it seals the outer pores, thus severely impairing the sound-absorbing and drainage properties of the material. If, however, a low-viscosity adhesive is used, it flows very quickly, not only downwards but also sideways, so that a large amount of it never reaches the area to be hardened. On the other hand, the use of low-viscosity adhesives has the advantage that the adhesive penetrates even into very small pores and narrow gaps, thus ensuring that the pieces of the heaped structure adhere to each other on many contact points.
Even if one were to assume that it is possible to produce an adhesive with a very precise degree of viscosity, which is suitable for bonding the pieces of a certain heaped structure down to a certain depth, there are still other problems to be solved, namely that, over the application time, the viscosity curve usually changes as the adhesive hardens and that, in particular, uniform conditions do not exist under actual circumstances, since the material, the porosity, the temperature and other parameters are subject to fluctuations which have a great influence on the quality of the hardening whenever an adhesive of uniform viscosity is poured or sprayed in its liquid state onto the heaped structure.